How to create a child

Please read this link to learn how to create a child theme and the benefits of creating one. Basically a child theme allows you to make changes to a theme without worrying about losing those changes when the parent theme gets updated. That is, if you need to make changes to a template file (i.e., a .php file), then you would do it through a child theme. If you want to just add CSS rules to affect changes, then your other option would be to use a CSS plugin, instead, if the theme that you are using doesn’t have a Custom CSS option.